/Engine/Source/Runtime/TimeManagement/Public/TimeSynchronizationSource.h
Adds an integer offset (representing frames) to the given FrameTime. It's expected the offset's magnitude will be less than the rollover modulus.
static [FFrameTime](API\Runtime\Core\Misc\FFrameTime) AddOffsetWithRolloverModulus ( const [FFrameTime](API\Runtime\Core\Misc\FFrameTime) & FrameTime, const int32 Offset, const [FFrameTime](API\Runtime\Core\Misc\FFrameTime) & RolloverModulus )